Delay Correction（延遲校正）
放射性的衰減。由於圖像獲取的時間要晚於示蹤劑注射的時間，期間會發生放射性的衰減，所以有可能在參數計算的時候對圖像所獲得的計數進行校正，校正到示蹤劑注射的時間，稱為 zero time.
Radioactive decay during PET study can be accounted for either by decay correction of the measured PET data before further analysis, or by implementation of decay into the compartmental model.
在定量分析之前進行校正
clear all;
T = 6588; % F-18
lambda = log(2)./T;
A0 = 24;
t1 = 1800;
dt = 600;
t2 = t1+600;
tt = linspace(0,6588,6589);
fun = @(t) A0*exp(-lambda*t);
rectangle(Position,[t1,0,dt,fun((t1+t2)./2)],LineWidth,1,LineStyle,-,FaceColor,[0,0.5,0.5]);
hold on;
plot([t1,t1],[0,fun(t1)],r);
plot([t2,t2],[0,fun(t2)],r);
plot(tt,fun(tt),r);
Decay correction
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